Hi Maja,
(forwarding to the address that should be used for for Chimera questions)
It is probably just too big for the memory on your computer to open this structure in Chimera.
Depending on what you’re trying to do with this capsid, maybe you could try using ChimeraX instead of Chimera. It handles large structures much more efficiently, but it does not have the same set of features as Chimera.
If you are just trying to get the atomic coordinates of the entire capsid, they are already in the file(s) you could download directly from the RCSB PDB without using any visualization program.
Best,
Elaine
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Elaine C. Meng, Ph.D.
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco